Method of making fluoropolymers

ABSTRACT

A process for making a fluoropolymer is disclosed. The process comprises solubilizing a fluoromonomer in solvent comprising a carbon dioxide fluid, and then polymerizing the fluoromonomer to produce a the fluoropolymer. A preferred solvent for carrying out the process is supercritical carbon dioxide; preferred fluoromonomers for carrying out the process are fluoroacrylate monomers such as 1,1-dihydroperfluorooctyl acrylate. The polymerization step is preferably carried out in the presence of an initiator such as azobisisobutyronitrile.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.08/302,642, filed Sep. 27, 1994, now U.S. Pat. No. 5,496,901 which is acontinuation under 35 USC §371 of PCT Application Ser. No.PCT/US93/01626, filed Feb. 26, 1993, which is a continuation-in-part ofU.S. patent application Ser. No. 07/858,150, filed Mar. 27, 1992, nowabandoned.

FIELD OF THE INVENTION

The present invention relates to a method of making fluoropolymers,including copolymers thereof, in a solvent comprising a carbon dioxidefluid such as supercritical carbon dioxide.

BACKGROUND OF THE INVENTION

Chlorofluorocarbons (CFCs) have been identified as one of the maincauses of the depletion of atmospheric ozone. As a result, extensiveeffort has been directed towards discovering alternatives to CFCs in avariety of applications. In addition to the utilization of CFCs asrefrigerants and aerosols, CFCs are commonly used as solvents for themanufacture of fluoropolymers, which are generally insoluble intraditional organic solvents but can often be solubilized in CFCs.Hence, there is a need for alternative methods of manufacturingfluoropolymers.

A supercritical fluid (SCF) is a substance above its criticaltemperature and critical pressure (or "critical point"). Compressing agas normally causes a phase separation and the appearance of a separateliquid phase. However, if the fluid is in a supercritical state,compression will only result in density increases: no liquid phase willbe formed. The physical properties of supercritical fluids are highlyunpredictable, and the use of supercritical fluids for carrying outpolymerization processes has received relatively little attention.

S. Kumar et al., Polym. Prep. 27, 224 (1986), describe the free radicalprecipitation polymerization of polystyrene chains in supercriticalethane. The styrene monomers were dissolved in ethane and polymerizedwith azobisisobutyronitrile ("AIBN") as an initiator using an apparatushaving a high-pressure optical cell.

V. Sarai and E. Kiran, Polym. Prep. 31, 687 (1990), describe the freeradical polymerization of styrene in supercritical ethane, propane, andbutane, using AIBN, t-butyl peroxide and t-butyl peroxybenzoate asinitiators.

K. Scholsky, Polym. Prep. 31, 685 (1990), describe a variety ofpolymerization reactions using supercritical fluids. The articlesummarizes publications on the polymerization of fluorinated olefins,such as vinyl fluoride, tetrafluoroethylene, the copolymerization oftetrafluoroethylene and sulfur dioxide, and polyperfluoropropylene.Other fluorinated olefins mentioned include n-tetradecafluoroheptene-1,n-perfluoropentadiene-1,4, vinylidene chlorofluoride, and a variety ofvinylic monomers. The polymerization of fluoropolymers in carbon dioxideis not suggested.

E. Beckman and R. Smith, J. Phys. Chem. 94, 345 (1990) describe themicroemulsion polymerization of acrylamide (CH₂ CHCONH₂) insupercritical fluids, and particularly the inverse microemulsionpolymerization of water-soluble acrylamide monomers within near-criticaland supercritical alkane continuous phases.

G. S. Varadarajan, Free Radical Polymerization in Supercritical FluidSolvents (Nov. 29, 1990) (MIT Doctoral Thesis) describes the freeradical polymerization of polymethylmethacrylate (MMA) (CH₂═C(CH₃)COOCH₃) in supercritical carbon dioxide using AIBN as aninitiator. The polymerization of fluoromethacrylates in supercriticalcarbon dioxide is not suggested.

Canadian Patent No. 1,274,942 is directed to acrylic acid polymerizationby homopolymerizing carboxylic acids such as acrylic acid andmethacrylic in supercritical carbon dioxide. The polymerization offluoroacrylate or fluoromethacrylate monomers in supercritical carbondioxide is not suggested.

V. Krukonis and M. McHugh, Supercritical Fluid Extraction, 156-158,describes the fractionation of a perfluoroalkylpolyether oil and achlorotrifluoroethylene oligomer in supercritical carbon dioxide, butdoes not suggest the polymerization of fluoromonomers in supercriticalcarbon dioxide.

SUMMARY OF THE INVENTION

A process for making a fluoropolymer is disclosed. The process comprisessolubilizing a fluoromonomer in a solvent, the solvent comprising carbondioxide fluid; and then polymerizing the fluoromonomer in said solventto produce said fluoropolymer. The fluoromonomer may be a fluoroacrylatemonomer, a fluorostyrene monomer, a fluorinated vinyl ether monomer, ora fluoroalkylene oxide oligomer. Fluoromonomers of the type whichundergo free radical polymerization are preferred. The polymerizationreaction is, in general, carried out in the presence of an initiator.The carbon dioxide fluid may be liquid carbon dioxide or supercriticalcarbon dioxide.

In one embodiment of the foregoing, the process may further comprisesolubilizing a comonomer in the carbon dioxide fluid, with thepolymerizing step comprises copolymerizing the fluoromonomer with thecomonomer.

The fluoropolymers can be used as a composition for altering surfacetension properties, e.g., to create low energy surfaces such as forstain resistance properties.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings which form a part of the disclosure of the invention:

FIG. 1 is a phase equilibria diagram of Poly(chlorotrifluoroethylene) incarbon dioxide at 40° C., wherein the x axis of the diagram representsthe weight fraction of the sample, and the y axis represents pressure inbars; and

FIG. 2 is a phase equilibria diagram of Poly(1,1-dihydroperfluorooctylacrylate) in carbon dioxide at 60° C., wherein the x axis of the diagramrepresents the weight fraction of the sample, and the y axis representspressure in bars.

DETAILED DESCRIPTION OF THE INVENTION

The term "fluoropolymer," as used herein, has its conventional meaningin the art. See generally Fluoropolymers (L. Wall, Ed. 1972)(Wiley-Interscience Division of John Wiley & Sons); see alsoFluorine-Containing Polymers, 7 Encyclopedia of Polymer Science andEngineering 256 (H. Mark et al. Eds., 2d Ed. 1985). Likewise, the term"fluoromonomer" refers to fluorinated precursor monomers employed in thesynthesis of fluoropolymers. The term "solubilizing," as used herein, isused to indicate that the fluoromonomers are in the same phase as thecarbon dioxide fluid in the process of the present invention; hence thepolymerization reactions of the present invention are solutionpolymerizations, as opposed to heterogeneous polymerizations or bulkpolymerizations, with these terms having their ordinary meaning in theindustry. See, e.g., G. Odian, Principles of Polymerization, 301-334 (3dEd. 1991) (Wiley Interscience).

Any suitable fluoromonomer may be used, including, but not limited to,fluoroacrylate monomers, fluoroolefin monomers, fluorostyrene monomers,fluoroalkylene oxide monomers (e.g., perfluoropropylene oxide,perfluorocyclohexene oxide), fluorinated vinyl alkyl ether monomers, andthe copolymers thereof with suitable comonomers, wherein the comonomersare fluorinated or unfluorinated. Fluoromonomers which are polymerizedby a free radical polymerization process are preferred.

Fluorostyrenes and fluorinated vinyl alkyl ether monomers which may bepolymerized by the method of the present invention include, but are notlimited to, α-fluorostyrene; β-fluorostyrene; α,β-difluorostyrene;β,β-difluorostyrene; α,β,β-trifluorostyrene; α-trifluoromethylstyrene;2,4,6-Tris(trifluoromethyl)styrene; 2,3,4,5,6-pentafluorostyrene;2,3,4,5,6-pentafluoro-αmethylstyrene; and2,3,4,5,6-pentafluoro-β-methylstyrene. These monomers are particularlyuseful as comonomers in the method of the present invention.

Tetrafluoroethylene copolymers which are amorphous or have low meltingpoints can be prepared by the method of the present invention andinclude, but are not limited to, tetrafluoroethylene-hexafluoropropylenecopolymers, tetrafluoroethylene-perfluorovinyl ether copolymers (e.g.,copolymers of tetrafluoroethylene with perfluoropropyl vinyl ether),tetrafluoroethylene-ethylene copolymers, and perfluorinated ionomers(e.g., perfluorosulfonate ionomers; perfluorocarboxylate ionomers).

Fluorocarbon elastomers (see. e.g., 7 Encyclopedia of Polymer Science &Engineering 257) are a group of amorphous fluoroolefin polymers whichcan be produced by the process of the present invention and include, butare not limited to, poly(vinylidene fluoride-co-hexafluoropropylene);poly(vinylidene fluoride-co-hexafluoropropylene-co-tetrafluoroethylene);poly vinylidene fluoride-co-tetrafluoroethylene-co-perfluoro(methylvinyl ether)!; poly tetrafluoroethylene-co-perfluoro(methyl vinylether)!; poly(tetrafluoroethylene-co-propylene; and poly(vinylidenefluoride-co-chlorotrifluoroethylene).

The term "fluoroacrylate monomer," as used herein, refers to esters ofacrylic acid (H₂ C═CHCOOH) or methacrylic acid (H₂ C═CCH₃ COOH), wherethe esterifying group is a fluorinated group such as perfluoroalkyl. Aspecific group of fluoroacrylate monomers useful in the method of theinvention are compounds represented by formula (I):

    H.sub.2 C═CR.sup.1 COO(CH.sub.2).sub.n R.sup.2         (I)

wherein:

n is 1 or 2;

R¹ is hydrogen or methyl; and

R² is a perfluorinated aliphatic or perfluorinated aromatic group, suchas a perfluorinated linear or branched, saturated or unsaturated C1 toC10 alkyl, phenyl, or naphthyl.

In a particular embodiment of the invention, R² is a C1 to C8perfluoroalkyl or --CH₂ NR³ SO₂ R⁴, wherein R³ is C1-C2 alkyl and R⁴ isC1 to C8 perfluoroalkyl.

The term "perfluorinated," as used herein, means that all or essentiallyall hydrogen atoms on an organic group are replaced with fluorine.

Monomers illustrative of Formula (I) above, and their abbreviations asused herein, include the following:

2-(N-ethylperfluorooctanesulfonamido) ethyl acrylate ("EtFOSEA");

2-(N-ethylperflooctanesulfonamido) ethyl methacrylate ("EtFOSEMA");

2-(N-methylperfluorooctanesulfonamido) ethyl acrylate ("MeFOSEA");

2-(N-methylperflooctanesulfonamido) ethyl methacrylate ("MeFOSEMA");

1,1-Dihydroperfluorooctyl acrylate ("FOA"); and

1,1-Dihydroperfluorooctyl methacrylate ("FOMA").

In the process of the invention, the fluoroacrylate monomers may bepolymerized in the presence of a free radical polymerization initiator.Any of the various organic and inorganic initiators which are known forthe polymerization of monomers can be used, so long as it is compatiblewith carbon dioxide. The polymerization is carried out at two differenttemperatures by first subjecting the monomers to initial polymerizationat a lower temperature, and then completing the polymerization at asubstantially higher temperature.

Organic free radical initiators are preferred and include, but are notlimited to, the following: acetylcyclohexanesulfonyl peroxide; diacetylperoxydicarbonate; dicyclohexyl peroxydicarbonate; di-2-ethylhexylperoxydicarbonate; tert-butyl perneodecanoate; 2,2'-azobis(methoxy-2,4-dimethylvaleronitrile; tert-butyl perpivalate; dioctanoylperoxide; dilauroyl peroxide; 2,2'-azobis (2,4-dimethylvaleronitrile);tert-butylazo-2-cyanobutane; dibenzoyl peroxide; tert-butylper-2-ethylhexanoate; tert-butyl permaleate; 2,2-azobis(isobutyronitrile); bis(tert-butylperoxy)cyclohexane;tert-butylperoxyisopropylcarbonate; tert-butyl peraceatate; 2,2-bis(tert-butylperoxy)butane; dicumyl peroxide; ditertamyl peroxide;di-tert-butyl peroxide; p-menthane hydroperoxide; pinane hydroperoxide;cumene hydroperoxide; and tert-butyl hydroperoxide. Preferably, theinitiator is azobisisobutyronitrile ("AIBN").

The process of the invention is carried out in a carbon dioxide fluid,e.g., carbon dioxide in a liquid or supercritical state. As will beappreciated by those skilled in the art, all gases have a criticaltemperature above which the gas cannot be liquified by increasingpressure, and a critical pressure or pressure which is necessary toliquify the gas at the critical temperature. For example, carbon dioxidein its supercritical state exists as a form of matter in which itsliquid and gaseous states are indistinguishable from one another. Forcarbon dioxide, the critical temperature is about 31° C. (88° F.) andthe critical pressure is about 73 atmospheres or about 1070 psi. Theterm "supercritical carbon dioxide" as used herein refers to carbondioxide at a temperature greater than about 31° C. and a pressure ofgreater than about 1070 psi.

Liquid carbon dioxide may be obtained at temperatures of from about -15°C. to about -55° C. and pressures of from about 77 psi to about 335 psi.

One or more solvents and blends thereof may optionally be included inthe carbon dioxide. Illustrative solvents include, but are not limitedto, tetrahydrofuran, cyclohexane, and methanol. Such solvents aretypically included in an amount, by weight, of up to about 20%.

The polymerization initiators are used in the amounts conventionallyemployed for polymerization. For example, the initiator may be used inan amount of about 0.01 to 10, preferably about 0.01 to 5, parts byweight per 100 parts by weight monomer.

The polymerization reaction may be carried out at a temperature of about-55° C. to about 300° C., and is typically carried out at a temperatureof about -30° to 100° C. The reaction may be carried out at a pressureranging from about 15 psi to about 45000 psi, and is typically at apressure of from about 500 psi to about 10000 psi.

In alternative embodiments of the present invention, at least onemonomer or comonomer is solubilized in carbon dioxide and copolymerizedwith the fluoromonomer. Any suitable monomers or comonomers can beemployed, including, but not limited to, acrylate, methacrylate,acrylamide, methacrylamide, styrenics, ethylene, and vinyl ethermonomers. The copolymerizations of the present invention may be carriedout under temperature and pressure conditions similar to those givenabove.

The polymerization can be carried out batchwise or continuously withthorough mixing of the reactants in any appropriately designed highpressure reaction vessel (i.e., capable of withstanding pressures up to45000 psi). To remove the heat evolved during the polymerization,advantageously the pressure apparatus includes a cooling system.Additional features of the pressure apparatus used in accordance withthe invention include heating means such as an electric heating furnaceto heat the reaction mixture to the desired temperature and mixingmeans, i.e., stirrers such as paddle stirrers, impeller stirrers, ormultistage impulse countercurrent agitators, blades, and the like.

The polymerization can be carried out, for example, by placing themonomer and initiator in the pressure apparatus and introducing carbondioxide in liquid form. The reaction vessel is closed and the reactionmixture brought to the polymerization temperature and pressure.Alternatively, only a part of the reaction mixture may be introducedinto an autoclave and heated to the polymerization temperature andpressure, with additional reaction mixture being pumped in at a ratecorresponding to the rate of polymerization. In another possibleprocedure, some of the monomers are initially taken into the autoclavein the total amount of carbon dioxide and the monomers or comonomers arepumped into the autoclave together with the initiator at the rate atwhich the polymerization proceeds.

When the polymerization is complete the reaction mixture is cooled (ifnecessary), the carbon dioxide separated off (e.g., by simply venting tothe atmosphere), and the polymer collected. After separation of thecarbon dioxide, the polymer can be collected simply by physicalisolation, or by dissolution and precipitation, for example, by addingFreon-113™ or α,αα-trifluorotoluene to the polymer to dissolve thepolymer and recover it from the reaction vessel and then precipitatingthe same with methanol.

The following Examples are provided to further illustrate the presentinvention. In the Examples, SCF means supercritical fluid; AIBN meansazobisisobutyronitrile; MMA means polymethyl-methacrylate; psi meanspounds per square inch; g means grams; mg means milligrams; mL meansmilliliters; min means minutes; Mw means weight average molecularweight; Mn means number average molecular weight; MWD means molecularweight distribution (Mw/Mn); mmol means millimoles; dL/g meansdeciliters per gram; cm means centimeters; THF means tetrahydrofuran;DMF means N,N-dimethylformamide; DMAc means N,N-dimethylacetamide; n!means intrinsic viscosity; NMR means nuclear magnetic resonance; GPCmeans gel permeation chromatography; FTIR means fourier transforminfrared; IR means infrared; and temperatures are given in degreescelsius. These examples are illustrative of the invention, and shouldnot be construed as limiting thereof.

EXAMPLES 1-17 Solubility, Polymerization and Copolymerization ofFluoroacrylate Monomers EXAMPLE 1 Experimental Procedures

Materials. Five fluoromonomers, illustrated by Formula (II) and Table 1and Formula (III) and Table 2, were kindly provided by Minnesota Miningand Manufacturing Company (3M). MeFOSEA, EtFOSEA and EtFOSEMA werepurified by recrystallization in methanol. 1,1-Dihydroperfluorooctylacrylate (FOA) was purified by running through Al₂ O₃ column to removethe inhibitor. AIBN (Kodak) was recrystallized twice from methanol.Carbon dioxide (Matheson, 99.99%) was passed through copper oxidecatalyst column to remove trace amounts of oxygen and then through amolecular sieve(3A) column to remove trace amounts of moisture.Freon-113 (CF₂ ClCFCl₂) was fractionally distilled before use. Methanol(Mallinckrodt) was used as received.

                  TABLE 1                                                         ______________________________________                                         ##STR1##                                                                     Fluorinated Monomers of Formula (II)                                          Name             R          R'                                                ______________________________________                                        MeFOSEA          H          CH.sub.3                                          EtFOSEA          H          CH.sub.2 CH.sub.3                                 MeFOSEMA         CH.sub.3   CH.sub.3                                          EtFOSEMA         CH.sub.3   CH.sub.2 CH.sub.3                                 ______________________________________                                    

                  TABLE 2                                                         ______________________________________                                         ##STR2##                                                                     Fluorinated Monomers of Formula (III)                                                 Name          R                                                       ______________________________________                                                FOA           H                                                               FOMA          CH.sub.3                                                ______________________________________                                    

EXAMPLE 2 Comparative Example: Polymerization in Freon 113

Before running polymerizations in supercritical carbon dioxide, a seriesof poly(perfluoroalkyl acrylate)s and poly(perfluoroalkyl methacrylate)swere prepared using free radical polymerization methods in Freon-113 andin α,α,α-trifluorotoluene and studied their solubility in both liquidand supercritical carbon dioxide. The fluoromonomers employed for thisstudy are those set forth in Tables 1 and 2 above. The polymerizationconditions (feed ratios of monomers, initiator and solvents), intrinsicviscosities and molecular weight data are summarized at Table 3.

A typical procedure is described below. EtFOSEA (5 g),azobisisobutyronitrile (AIBN) (10 mg) and 10 mL of Freon-113 were putinto a 50 mL test tube. After sealing the tube with a rubber septum, thesolution was purged with argon for ca. 15 min, placed in a water bath at60° C. and left to polymerize for ca. 20 hours. The tube was opened nextday and ca. 30 mL of Freon-113 was added to dilute the polymer solution,followed by precipitation of polymer into methanol. The polymer wasfiltered and dried in vacuum oven overnight. All of the monomers werepolymerized in Freon-113 at 60° C. except MeFOSEA which was polymerizedin α,α,α-trifluorotoluene at 70° C. due to solubility considerations.

                                      TABLE 3                                     __________________________________________________________________________            Feed Ratio                                                                    monomer                                                                            AIBN                                                                              solvent                                                      Sample  (g)  (mg)                                                                              (ml)                                                                               n! Mw  Mn  MWD                                          __________________________________________________________________________    P(EtFOSEA)                                                                    910607-1                                                                              2     5  10  0.14                                                                              7.68e4                                                                            1.13e4                                                                            6.79                                         910607-2                                                                              2    10  10  0.11                                                                              9.23e4                                                                            1.32e4                                                                            7.02                                         910607-3                                                                              2    20  10   0.078                                                                            7.67e4                                                                            2.06e4                                                                            3.73                                         910614-0                                                                              3    2 + 2                                                                              2  0.44                                                                              1.24e5                                                                            5.14e4                                                                            2.41                                         910614-1                                                                              5     5  10  0.28                                                                              1.14e5                                                                            1.39e4                                                                            8.20                                         910614-2                                                                              5    10  10  0.28                                                                              1.56e5                                                                            5.56e4                                                                            2.80                                         910614-3                                                                              5    20  10  0.24                                                                              1.38e5                                                                            5.46e4                                                                            2.54                                         P(EtFOSEMA)                                                                   910710-3                                                                              5     5  10  0.13                                                                              7.20e4                                                                            8.23e3                                                                            8.75                                         P(FOA)                                                                        910710-1                                                                              5     5  10  0.21                                                                              1.10e6                                                                            2.90e5                                                                            3.78                                         P(FOMA)                                                                       910710-2                                                                              5     5  10  gel-                                                                          like                                                     910711  5     5  20   0.26*                                                                            unable                                                                        to                                                                            filter                                               P(MeFOSEA)**                                                                  910620-1                                                                              5    10  20   0.077                                                   910620-2                                                                              5    20  20   0.066                                                   910620-3                                                                              5    30  20   0.010                                                   __________________________________________________________________________     All polymerizations are run at 60° C.                                  *The viscosity of the soluble part.                                           **Polymerized in , , trifluorotoluene.                                   

EXAMPLE 3 Solubility Evaluation in Carbon Dioxide

The solubilities of poly(EtFOSEA) and poly(MeFOSEA) in carbon dioxidewere measured using a flow system, the results of which are set forth atTable 4. Poly(EtFOSEA) was found to be very soluble in both liquid andsupercritical carbon dioxide (about 25 wt. %). Poly(MeFOSEA) dissolvedin liquid CO₂ at 3000 psi at room temperature. A view cell studydiscussed below verified that the polymer was also soluble insupercritical CO₂.

For comparison, the solubility of poly(methyl methacrylate) (PMMA) inboth liquid and supercritical CO₂ was also studied. Quite differently,PMMA of even lower molecular weight than the two fluoropolymersdiscussed above is insoluble in carbon dioxide with the pressure rangingfrom 2000 to 5000 psi and temperature ranging from room temperature to160° C.

To ensure that the fluoropolymers form homogeneous solutions with carbondioxide, the solubility of the five fluoropolymers was also determinedusing a view cell. The results of the observations are set forth atTable 5. We observed that all the polymers dissolved and formed clearsolutions in carbon dioxide at moderate pressures. Comparatively,poly(FOA) and poly(FOMA) are easier to dissolve in carbon dioxide thanpoly-(EtFOSEMA), poly(EtFOSEA) and poly(MeFOSEA), but all of thepolymers dissolve.

                                      TABLE 4                                     __________________________________________________________________________    Solubility study of F-polymers by flow system:                                                                Solubility                                    Sample  n! M.sub.w × 10.sup.-5                                                          M.sub.n × 10.sup.-4                                                          T(°C.)                                                                      P(psi)                                                                              (wt. %)                                       __________________________________________________________________________    P(EtFOSEA)                                                                           0.44                                                                              1.24 5.14 29   5000  25                                            P(EtFOSEA)                                                                           0.28                                                                              1.14 1.39 60   4000  25                                            P(MeFOSEA)                                                                            0.077                                                                            --   --   25   3000  15-20                                         PMMA   --  0.22 1.93  29-160                                                                            2000-5000                                                                           0                                             __________________________________________________________________________

                  TABLE 5                                                         ______________________________________                                        Solubility study of F-polymers by view cell:                                                                              Conc.                                                                         wt. %                             Sample    n!     M.sub.w × 10.sup.-5                                                              M.sub.n × 10.sup.-4                                                            T(°C.)                                                                       P(psi)                                                                             vol                               ______________________________________                                        P(EtFOSEA)                                                                             0.44    1.24     5.14   25    7000 9                                 P(EtFOSEA)                                                                             0.24    1.38     5.46   25    3000 5                                 P(MeFOSEA)                                                                              0.077  --       --     60    3700 5                                 P(FOA)   0.21    11.0     29.0   25    2000 5                                 P(FOA)   0.21    11.0     29.0   25    3000 10                                P(FOMA)  0.26    --       --     25    2000 5                                 P(EtFOSEMA)                                                                            0.13    0.72     0.82   25    4000 5                                 ______________________________________                                         *Pressure at which the polymer totally dissolve.                         

EXAMPLE 4 Polymerization of 1,1-dihydroperfluorooctyl Acrylate (FOA) inCarbon Dioxide

FOA (5.0 g 11.0 mmol, purified by running through Al₂ O₃ column) andAIBN (50 mg, 0.30 mmol, recrystallized twice from methanol) were putinto a 10 ml high pressure reaction cell with a micromagnetic stir barinside. The reaction cell was purged with argon for ca. 10 minutes andthen filled with carbon dioxide to a pressure of less than 1000 psi.Over a period of one hour, the cell was heated to 60° C. and thepressure was increased to 3000 psi by the addition of more CO₂. Thepolymerization was continued at these conditions for 48 hours, duringwhich the system was homogeneous and clear.

At the end of the polymerization, carbon dioxide was vented slowly toleave the polymer in the cell. The polymer was dissolved with Freon-113and was precipitated into a large excess of methanol. The polymer wasisolated by suction filtration, washed several times with methanol, anddried in vacuo overnight to give 3.25 g of transparent viscous polymer(yield: 65%).

Characterizations: ¹ H NMR spectrum showed the expected pattern, withoutvinyl proton peaks of the monomer and without any indication ofincorporation of carbon dioxide onto the polymer backbone. The intrinsicviscosity was measured to be 0.19 dL/g in Freon-113 at 30° C. The FTIRspectrum was consistent with the corresponding homopolymer made inFreon-113, with only one carbonyl peak at 1758 cm⁻¹.

EXAMPLE 5 Polymerization of FOA in carbon dioxide

FOA (2.0 g, 4.4 mmol) and AIBN (30 mg, 0.18 mmol) were put into the highpressure cell. Following the same procedure as described in Example 4,polymerization was proceeded at 3000 psi and 60° C. for 24 hours, and0.41 g of polymer was obtained (yield: 21%).

Characterizations: ¹ H NMR and FTIR spectra were consistent with thoseof the homopolymer made in Freon-113.

EXAMPLE 6 Polymerization of 1,1-dihydroperfluorooctyl Methacrylate(FOMA) in Carbon Dioxide

FOMA (3.0 g, 6.41 mmol, purified by running through Al₂ O₃ column) andAIBN (30 mg, 0.18 mmol) were put into the 10 mL high pressure reactioncell. The reaction cell was purged with argon for ca. 10 minutes thenfilled with carbon dioxide to a pressure of less than 1000 psi. Over aperiod of one hour, the cell was heated to 60° C., and the pressure wasincreased to 4000 psi by the addition of more CO₂. The polymerizationwas continued at these conditions for 48 hours, during which the systemwas homogeneous and clear. At the end of the polymerization, carbondioxide was vented slowly to leave the polymer in the cell. The polymerwas dissolved with Freon-113 and was precipitated into a large excess ofmethanol. The polymer was isolated by suction filtration, washed severaltimes with methanol, and dried in vacuo overnight to give 2.19 g of awhite powder (yield: 73%).

Characterizations: ¹ H NMR and FTIR spectra were consistent with thoseof the same polymer made in Freon-113. The intrinsic viscosity wasmeasured to be 0.06 dL/g in Freon-113 at 30° C.

EXAMPLE 7 Polymerization of FOMA in CO₂

FOMA (5.0 g, 10.7 mmol) and AIBN (50 mg, 0.3 mmol) was put into the 10mL high pressure cell. Following the same procedure described in Example4, the polymerization was carried out in CO₂ at 60° C. and 5000 psi for48 hours. During the entire course of the polymerization, the solutionwas homogeneous and clear. The polymer was isolated according to thesame procedure as described above.

Characterizations: ¹ H NMR and FTIR spectra were consistent with thoseof the same polymer made in Freon-113. The intrinsic viscosity wasmeasured to be 0.06 dL/g in Freon-113 at 30° C.

EXAMPLE 8 Polymerization of 2-(N-methylperfluorooctane-sulfonamido)ethyl Acrylate (MeFOSEA) in Carbon Dioxide

MeFOSEA (5.0 g, 8.75 mmol, purified by recrystallization from methanol)and AIBN (50 mg, 0.30 mmol) were put into the 10 mL high pressurereaction cell. The reaction cell was purged with argon for ca. 10minutes then filled with carbon dioxide to a pressure of less than 1000psi. Over a period of one hour the cell was heated to 60° C. and thepressure was increased to 5000 psi by the addition of more CO₂. Thepolymerization was continued at these conditions for 48 hours, duringwhich the system was homogeneous and clear. At the end of thepolymerization, carbon dioxide was vented slowly to leave the polymer inthe cell. The polymer was dissolved in α,α,α-trifluorotoluene and wasprecipitated into a large excess of methanol. The polymer was isolatedby suction filtration, washed several times with methanol, and dried invacuo overnight to give 3.2 g of white powder (yield: 64%).

Characterizations: FTIR spectra were consistent with those of the samepolymer made in Freon-113.

EXAMPLE 9 Polymerization of MeFOSEA in Carbon Dioxide

MeFOSEA (1.0 g, 1.75 mmol) and AIBN (10 mg, 0.06 mmol) were put into thehigh pressure cell. Following the same procedure of Example 4, thepolymerization was proceeded under 4000 psi and 60° C. for 8 hours, and0.19 g of polymer was obtained (yield: 19%).

Characterizations: FTIR spectrum were consistent with the same polymermade in Freon-113. The intrinsic viscosity was measured to be 0.064 inα,α,α-trifluorotoluene at 70° C.

EXAMPLE 10 Polymerization of 2-(N-ethylperfluorooctane-sulfonamido)Ethyl Acrylate (EtFOSEA) in Carbon Dioxide

EtFOSEA (5.0 g, 8.53 mmol, purified by recrystallization from methanol)and AIBN (50 mg, 0.30 mmol) were put into the 10 mL high pressure viewcell. The reaction cell was purged with argon for ca. 10 minutes thenfilled with carbon dioxide to a pressure of less than 1000 psi. Over aperiod of one hour the cell was heated to 60° C. and the pressure wasincreased to 5000 psi by the addition of more CO₂. The polymerizationwas continued at these conditions for 48 hours, during which the systemwas homogeneous and clear. At the end of the polymerization, carbondioxide was vented slowly to leave the polymer in the cell. The polymerwas dissolved in Freon-113 and was precipitated into a large excess ofmethanol. The polymer was isolated by suction filtration, washed severaltimes with methanol, and dried in vacuo overnight to give 3.9 g of awhite powder (yield: 78%).

Characterizations: ¹ H NMR and FTIR spectra were consistent with thoseof the same polymer made in Freon-113. The intrinsic viscosity wasmeasured to be 0.20 dL/g in Freon-113 at 30° C. Both the polymers madein CO₂ and in Freon-113 were purified by dissolving in Freon-113 andreprecipitating into methanol and an elemental analysis by ORS wasperformed. The results are summarized in Table 6 below.

                  TABLE 6                                                         ______________________________________                                        Elemental Analysis of Poly(EtFOSEA) Made in                                   Carbon Dioxide and in Freon-113                                               Sample   % C       % H    % N     % F  % S                                    ______________________________________                                        P-Freon  28.69     1.86   2.21    51.47                                                                              5.05                                   P-CO.sub.2                                                                             28.80     1.91   2.24    50.78                                                                              4.81                                   Calculated                                                                             29.01     2.01   2.33    50.64                                                                              5.34                                   ______________________________________                                    

EXAMPLE 11 Polymerization of 2-(N-ethylperfluorooctane-sulfonamido)Ethyl Methacrylate (EtFOSEMA) in CO₂

EtFOSEMA (5.0 g, 8.33 mmol, purified by recrystallization from methanol)and AIBN (50 mg, 0.30 mmol) were put into the same reaction vessel. Thereaction vessel was purged with argon for ca. 10 minutes then filledwith carbon dioxide to a pressure of less than 1000 psi. Over a periodof one hour the cell was heated to 60° C., and the pressure wasincreased to 5000 psi by the addition of more CO₂. The polymerizationwas continued at these conditions for 48 hours, during which the systemwas homogeneous and clear. At the end of the polymerization, carbondioxide was vented slowly to leave the polymer in the vessel. Thepolymer was dissolved in Freon-113 and was precipitated into a largeexcess of methanol. The polymer was isolated by suction filtration,washed several times with methanol, and dried in vacuo overnight to give3.2 g of white powder.

Characterizations: ¹ H NMR and FTIR spectra were consistent with thoseof the same polymer made in Freon-113. The intrinsic viscosity wasmeasured to be 0.10 dL/g in Freon-113 at 30° C.

EXAMPLE 12 Copolymerization of FOA with Methyl Methacrylate (MMA) in CO₂

FOA (4.0 g, mmol, purified by running through Al₂ O₃ column), MMA (1.0g, 10.0 mmol, purified by vacuum distillation over CaH₂) and AIBN (50mg, 0.30 mmol) were put into the 10 mL high pressure view cell. Thereaction cell was purged with argon for ca. 10 minutes then filled withcarbon dioxide to less than 1000 psi. Over a period of one hour the cellwas heated to 60° C. and the pressure was increased to 5000 psi by theaddition of more CO₂. The polymerization was continued at theseconditions for 48 hours, during which the system was homogeneous andclear. At the end of the polymerization, carbon dioxide was ventedslowly to leave the polymer in the cell. The polymer was dissolved inFreon-113 and was precipitated into a large excess of methanol. Thepolymer was isolated by suction filtration, washed several times withmethanol, and dried in vacuo overnight to give 3.25 g of copolymer(yield: 65%). The copolymer was extracted with THF three times to removeany possible PMMA homopolymer.

Characterizations: Solubility of the copolymer in normal solvents andFreon-113 was checked and the results are summarized in Table 7 below.

                  TABLE 7                                                         ______________________________________                                        Solubility Test of PFOA-co-PMMA-1                                             Solvent         solubility                                                    ______________________________________                                        Freon-113       soluble, but slightly cloudy                                  acetone         liquified but insoluble                                       THF             liquified but insoluble                                       CH.sub.2 Cl.sub.2                                                                             swelled                                                       toluene         swelled                                                       DMF             slightly swelled                                              DMAc            slightly swelled                                              ______________________________________                                    

¹ H NMR and FTIR spectra were indicative of a statistical or randomcopolymer. Composition of the copolymer was calculated to be 58 mol %FOA from the ¹ H NMR spectrum. IR spectrum showed two carbonyl peaks at1758 (carbonyl of FOA segments) and 1734 cm⁻¹ (carbonyl of MMAsegments), respectively. The intrinsic viscosity was measured to be 0.10dL/g in Freon-113 at ° C.

EXAMPLE 13 Copolymerization of FOA and MMA in Carbon Dioxide

FOA (3.0 g, 6.6 mmol, purified by running through A₂ O₃ column), MMA(2.0 g, 20.0 mmol, purified by vacuum distillation over CaH₂) and AIBN(50 mg, 0.30 mmol) were put into the high pressure cell. The reactioncell was purged with argon for ca. 10 minutes then filled with carbondioxide to less than 1000 psi. Over a period of one hour the cell washeated to 60° C. and the pressure was increased to 5000 psi by theaddition of more CO₂. The polymerization system became nonhomogeneousafter ca. 12 hours. After 48 hours, there existed two layers, with thebottom layer accounting for ca. 1/4 of the total reactor volume and acloudy upper layer accounting for ca. 3/4 of the total volume. At theend of the polymerization, carbon dioxide was vented slowly to leave thepolymer in the cell. The polymer was dissolved in Freon-113 and wasprecipitated into a large excess of methanol. The polymer was isolatedby suction filtration, washed several times with methanol, and dried invacuo overnight to give 3.3 g of copolymer (yield: 66%). The copolymerwas extracted with DMF three times.

Characterizations: ¹ H NMR and FTIR spectra show the expected patterns.Composition of copolymer was calculated from proton NMR spectrum to be27 mol % in FOA. Two carbonyl peaks appear on the IR spectrum (1758 and1734 cm⁻¹). The intrinsic viscosity was measured to be 0.12 dL/g inacetone at 30° C. The solubilities of the copolymer in normal solventsare summarized in Table 8 below.

                  TABLE 8                                                         ______________________________________                                        Solubility of PFOA-co-PMMA-2 in Different Solvents                            Solvent            Solubility                                                 ______________________________________                                        Freon-113          soluble                                                    acetone            soluble                                                    THF                soluble                                                    CHCl.sub.3         soluble                                                    CH.sub.2 Cl.sub.2  soluble  (40° C.)                                   toluene            soluble (100° C.)                                   DMF                insoluble                                                  DMAc               insoluble                                                  ______________________________________                                    

Since this copolymer is soluble in normal solvents, ¹³ C NMR and ¹⁹ FNMR spectra was measured in d6-acetone. Only two carbonyl peaks appearedon the spectrum (177, 178 ppm). The ¹⁹ F NMR spectrum showed sixresonances. GPC was run with THF as solvent and polystyrene as standard.The results were Mn=5.10×10⁴, Mw=7.45×10⁴, MWD=1.46.

EXAMPLE 14 Copolymerization of FOA and MMA in C₂ with THF as aCo-Solvent

FOA (3.0 g, 6.6 mmol), MMA (2.0 g, 20 mmol) and AIBN (50 mg, 0.30 mmol)were put into the high pressure cell. 1.0 mL (10 vol %) THF was addedinto the mixture. The reaction cell was purged with argon for ca. 10minutes and then filled with carbon dioxide to less than 1000 psi. Overa period of one hour the cell was heated to 60° C., and the pressure wasincreased to 5000 psi by the addition of more CO₂. The polymerizationwas continued at these conditions for 48 hours. The system washomogeneous for at least 30 hours at which time it became cloudy. Thesolution remained homogenous for a longer time than the polymerizationreaction conducted without the cosolvent (Example 13). At the end of thepolymerization, carbon dioxide was vented slowly to leave the polymer inthe cell. The polymer was dissolved in Freon-113 and was precipitatedinto a large excess of methanol. The polymer was isolated by suctionfiltration, washed several times with methanol, and dried in vacuoovernight to give 3.9 g of white polymer (yield: 78%).

Characterizations: GPC was run with THF as solvent. The results were:Mn=5.50×10⁴, Mw=8.23×10⁴, MWD=1.50.

EXAMPLE 15 Copolymerization of FOA and n-butyl

Acrylate (BA) in Carbon Dioxide

FOA (4.0 g, 6.6 mmol), BA (1.0 g, 7.8 mmol, purified by running throughAl₂ O₃ column) and AIBN (50 mg, 0.30 mmol) were put into the highpressure reaction cell. The reaction cell was purged with argon for ca.10 minutes then filled with carbon dioxide to less than 1000 psi. Over aperiod of one hour the cell was heated to 60° C. and the pressure wasincreased to 5000 psi by the addition of more CO₂. The polymerizationwas continued at these conditions for 48 hours, during which the systemwas homogeneous and clear. At the end of the polymerization, carbondioxide was vented slowly to leave the polymer in the cell. The polymerwas dissolved with Freon-113 and was precipitated into a large excess ofmethanol. The polymer was isolated by suction filtration, washed severaltimes with methanol, and dried in vacuo overnight to give a transparentelastic material which was purified by extracting with acetoneovernight.

Characterizations: ¹ H NMR and FTIR spectra were indicative of a randomor statistical copolymer. Composition of the copolymer was calculated tobe 59% FOA based on ¹ H NMR. Two carbonyl resonances appeared in the IRspectrum (1760 and 1720 cm³¹ 1). The intrinsic viscosity was 0.45 dL/gin Freon-113 at 30° C. The solubility of the copolymer is summarized inTable 9.

                  TABLE 9                                                         ______________________________________                                        The Solubility of PFOA-co-PBA in Different Solvents                           Solvent           Solubility                                                  ______________________________________                                        Freon-113         soluble                                                     acetone           insoluble                                                   THF               insoluble                                                   CHCl.sub.3        dispersed but insoluble                                     toluene           insoluble                                                   DMF               insoluble                                                   ______________________________________                                    

EXAMPLE 16 Copolymerization of FOA with Styrene in CO₂

FOA (4.0 g, 6.6 mmol), styrene (1.0 g, 9.6 mmol, purified by vacuumdistillation) and AIBN (50 mg, 0.30 mmol) were put into the highpressure reaction cell. The reaction cell was purged with argon for ca.10 minutes then filled with carbon dioxide to less than 1000 psi. Over aperiod of one hour the cell was heated to 60° C. and the pressure wasincreased to 5000 psi by the addition of more CO₂. The polymerizationwas continued at these conditions for 48 hours, during which the systemwas homogeneous and clear. At the end of the polymerization, carbondioxide was vented slowly to leave the polymer in the cell. The polymerwas dissolved with Freon-113 and was precipitated into a large excess ofmethanol. The polymer was isolated by suction filtration, washed severaltimes with methanol, and dried in vacuo overnight to give a very tackymaterial. The polymer was extracted with acetone overnight to remove anypossible styrene homopolymer.

Characterizations: ¹ H NMR and FTIR spectra were indicative of a randomor statistical copolymer. All the peaks of FOA were shifted upfield byca. 0.4 ppm. Also the peak of the methylene proton adjacent to theperfluoroalkyl chain was broadened. IR spectrum showed one carbonylresonance at 1758 cm⁻¹ and peaks appeared in the region between 3000 to3100 cm⁻¹ due to the stretching vibration of C--H on the phenyl ring ofthe styrene repeating unit.

EXAMPLE 17 Copolymerization of FOA with Ethylene in CO₂

FOA (4.0 g, 6.6 mmol) and AIBN (50 mg, o.30 mmol) were put into the highpressure cell. Ethylene (0.46 g, 16.4 mmol) was transferred from a smallbomb into the reaction cell. CO₂ was added, and the temperature wasraised to 60° C. and the total pressure was 5000 psi. The polymerizationwas allowed to proceed for ca. 48 hours. During this time period, thesystem remained homogeneous and clear. After venting CO₂, the productwas dissolved with Freon-113 and precipitated into large excess ofmethanol to give 2.9 g of viscous polymer (yield: 65%). The copolymerwas extracted with boiling toluene for two hours to remove anypolyethylene homopolymer.

Characterization: The copolymer was insoluble in acetone, toluene, THF,chloroform and DMF. It was soluble in Freon-113. ¹ H NMR spectrum showeda new peak appearing at ca. 1.5 ppm, which is presumably due to theprotons of the ethylene repeat unit. FTIR show similar pattern to PFOAhomopolymer. The resonance of ethylene repeat unit may be buried by theresonance of the backbone of FOA. Intrinsic viscosity was measured to be0.14 dL/g in Freon-113 at 30° C.

EXAMPLE 18 Cationic Polymerization of Vinyl Ethers in CO₂ Vinyl etherswith a fluoroalkyl group according to Formula (IV):

    R.sup.1 R.sup.2 C═CR.sup.3 O(CH.sub.2).sub.n R         (IV)

wherein:

n is 0, 1, or 2;

R¹, R², and R³ are each independently hydrogen or fluorine; and

R is perfluorinated aliphatic or perfluorinated aromatic group, forexample, CH₂ ═CH--OCH₂ CH₂ N(n--C₃ H₇)SO₂ C₈ F₁₇ or CH₂ ═CH--OCH₂ C₈F₁₇, are polymerized with an initiator such as boron trifluoroetherate,hydrogen iodine/iodine, and hydrogen iodine/zinc iodine in liquid andsupercritical carbon dioxide using the procedure of Example 4 above. Ithas previously been known that these monomers could be solventpolymerized in Freon. See W. Choi et al., Polymer J. 20, 201 (1988).Thus, this example indicates that the ability of a monomer to undergosolution polymerization in Freon-113 is a good indicator that themonomer can be polymerized in liquid or supercritical carbon dioxide.

EXAMPLE 19 Polymerization of 1,1-Disubstituted Monomers1,1-disubstituted monomers according to Formula (V): ##STR3## wherein Ris C1-C4 alkyl (e.g., ethyl) and R_(f) is (CF₂)_(n) F wherein n is 1-10,(e.g., CF₃, (CF₂)₂ F, (CF₂)₇ F, or (CF₂)₁₀ F), are polymerized in liquidor supercritical carbon dioxide under conditions using the procedure ofExample 4 above. EXAMPLE 20 Polymerization with Chain Transfer Agents

Functional fluoropolymers are produced in liquid or supercritical carbondioxide by polymerizing a fluoromonomer such as FOA in carbon dioxide inthe presence of a chain transfer agent such as substituted allylicsulfides. This results in fluoropolymers capped with a carboxy, hydroxy,trialkylsilyl, or amino groups.

EXAMPLE 21 Polymerization of Block Fluoropolymers

Block fluoropolymers are produced in liquid or supercritical carbondioxide using the procedure of Example 4 above, using pseudo-living freeradical polymerization routes. For example, FOA is polymerized in carbondioxide with nitroxides similar to that disclosed in U.S. Pat. No.4,581,429 or with oxygen-centered radical species generated fromhyponitrite, arenediazoate, or cyanate anions by reaction with electronacceptors such as arenediazonium ions or activated alkyl halides withsequential monomer additions, similar to Druliner, J. D., Macromolecules1991, 24, 6079.

EXAMPLE 22 Poly(perfluoroalkyl ether) Polymerization

Poly(perfluoroalkyl ether)s are made in liquid or supercritical carbondioxide using the procedure of Example 4 above. For example,perfluoropropylene oxide is polymerized using initiators derived fromalkali metal fluorides and an acid fluoride such as CF₃ CO--F in carbondioxide to yield viscous oils.

EXAMPLE 23 Preparation of Monomers

Styrene (Aldrich), methyl methacrylate (MMA) (Aldrich), acrylic acid(AA) (Aldrich) were purified by running through an alumina column anddeoxygenated before polymerization. N-Octyl acrylate (OA), octadecylmethacrylate (ODMA) and all the perfluoroalkyl acrylates described abovein Example 1 were purified in a similar fashion. Vinylidene fluoride(VF₂) (Aldrich, 99% +) and pentafluorostyrene (5FSt) (PCR Inc.) wereused as received. The styrene-based monomer carrying a fluorocarbonsegment, p-perfluoroalkylethyleneoxymethyl styrene (STF), was preparedby a phase-transfer-catalyzed etherification of fluorocarbon-substitutedalcohol with p-(chloromethyl) styrene: ##STR4##

EXAMPLE 24 Homopolymerization of Fluorostyrene Monomerp-perfluoroalkylethyleneoxymethyl Styrene (STF)

A typical example of a homopolymerization in supercritical CO₂ wasconducted as follows. STF (1.0 g, 1.72 mmol) and AIBN (30 mg,recrystallized twice from methanol) were put into a 10-mL high pressureview cell containing a micromagnetic stir bar. The reaction cell waspurged with argon for ca. 10 minutes, and then filled with CO₂ to lessthan 68 bar. The cell was heated to 60° C. and the pressure wasincreased to 345 bar by the addition of more CO₂. The polymerization wascontinued at these conditions for 3 days, during which time the systemremained homogeneous and optically transparent. At the end of thepolymerization, the cell was cooled to room temperature and CO₂ wasvented resulting in the precipitation of the polymer. The unreactedmonomer was extracted with dichloromethane. The polymer was dried toconstant weight and characterized (65% yield).

The other monomers (VF2, 5FSt, styrene, MMA, AA) were allhomopolymerized in supercritical carbon dioxide according to a proceduresimilar to that above; however, these polymers precipitated during thecourse of the reaction in CO₂ under the conditions described.

EXAMPLE 25 Homopolymerization of Fluorostyrene Monomer Fluorostyrenemonomers according to Formula (VI): ##STR5## wherein: R¹ and R² are eachindependently hydrogen, fluorine, or methyl;

R³ is hydrogen, fluorine, methyl or perfluoromethyl;

R⁴ is hydrogen, fluorine, or C1-C12 perfluorinated aliphatic group; and

the 2, 3, 5, and 6 positions of the aromatic styrene ring are eachindependently hydrogen or fluorine, are polymerized with an initiatorsuch as AIBN in liquid and supercritical carbon dioxide using theconcentrations and procedure of Example 24 above.

EXAMPLE 26 Copolymerization of Fluorinated Monomer (FluoroacrylateMeFOSEA) with Non-Fluorinated Comonomer (OA)

A copolymerization of the fluorinated monomers with non-fluorinatedmonomers in supercritical CO₂ was conducted as follows.2-(N-Methylperfluoro-octanesulfonamido) ethyl acrylate (MeFOSEA, 1.3 g,2.12 mmol), OA (0.70 g, 3.80 mmol) and AIBN (30 mg, 0.18 mmol) were putinto the 10-mL high pressure view cell. Following the procedure asdescribed above in Example 24, the copolymerization was continued at 60°C. and 345 bar for 24 hours. The system was homogeneous during theentire course of the polymerization. After venting the CO₂, thecopolymer was redissolved in Freon-113 and precipitated into largeexcess of methanol. The polymer was filtered and washed with methanolseveral times and dried in vacuo overnight to give 1.35 g of copolymer(68% yield).

The other non-fluorinated monomers are also copolymerized in a similarfashion.

EXAMPLE 27 Copolymerization of Fluorinated Monomer (Fluoroacrylate FOA)With Fluorinated Comonomer (Vinylidene Fluoride)

The 10-mL high pressure cell was loaded with 1,1-dihydroperfluorooctylacrylate (FOA, 3.0 g, 6.6 mmol) and AIBN (50 mg, 0.30 mmol). Afterpurging with argon thoroughly, the cell was connected to a VF₂ cylinder,3.02 of VF₂ (47.2 mmol) was transferred into the cell by cooling downthe cell in a dry ice/isopropanol bath. After warming the cell to roomtemperature, carbon dioxide was filled to ca. 68 bar. The heating of thecell was continued and more CO₂ was added until the cell reached 60° C.and 345 bar. The polymerization was continued at these conditions forca. 50 hours during which the system was homogeneous during the entirecourse of the reaction. The copolymer was obtained according to the samework-up procedure.

EXAMPLE 28 Polymerization of 1,1-difluoroethylene (VF₂)

A low molecular weight polymer or oligomer was made in carbon dioxide bypolymerizing 1,1-difluoroethylene (VF2) in the presence of aperfluoroalkyliodide. 1.0 g of C₄ F₉ I and 2.0 g of VF₂ was transferredinto a 10-mL stainless steel cell fitted with sapphire windows. The cellwas heated to 36° C. and filled to 3000 psi with carbon dioxide. Thereaction was homogeneous (optically transparent and colorless). The cellwas irradiated with an ultraviolet lamp for 24 hours, during which timethe reaction remained homogeneous and turned color from colorless tolight purple or pink. ##STR6##

The product distribution was determined by gas chromatography-massspectrometry to include the various products listed above with thevarious regioisomers as shown.

EXAMPLE 29

A low molecular weight polymer or oligomer is made in carbon dioxide bypolymerizing tetrafluoroethylene (TFE) using the concentrations andprocedures of Example 28 above, but in the presence of a chain transferagent such as trifluoromethyl iodide or IF to yield: ##STR7## underhomogeneous conditions in a stainless steel or Hastalloy reactor/viewcell.

EXAMPLE 30

Following the procedure set forth in Example 28 and 29 above,fluoroolefins, such as tetrafluoroethylene (TFE),chlorotrifluoroethylene (CTFE), hexafluoropropylene (HFP),perfluoro-2,2-dimethyl-1,3-dioxole or mixtures of these monomers, orwith the addition of ethylene monomer, are polymerized under homogeneousconditions in carbon dioxide.

EXAMPLE 31

Low molecular weight polymers or oligomers are made in carbon dioxideusing a process essentially as described in Examples 28, 29 and 30above, but the reaction product is endcapped with ethylene to yield:##STR8##

EXAMPLE 32

A dimer, oligomer or low molecular weight polymer of CTFE, HFP, TFE, orVF₂ is obtained by following the procedures of Example 28 above, exceptthat the fluoroolefin or mixtures of the fluoroolefins are treated withI₂ or another Lewis acid (such as FeCl₃) in carbon dioxide to form aproduct soluble in carbon dioxide. Halogenated chain transfer agents ortelogens such as Cl₃ CBr, CFCL₃, CFCL₃, CCl₄, Br--CFCL--CF₂ --Br areoptionally added. The reactions are optionally facilitated by UVirradiation or added peroxide.

EXAMPLE 33 Terpolymerization of Fluoroolefin Monomers

A fluoropolymer is made by terpolymerizing TFE, CTFE, and ethylene incarbon dioxide using a peroxide initiator and a chain transfer agentsuch as freon-11 and the following ratios of TFE/CTFE/Ethylene:20/45/35; 10/55/35; and 30/30/40.

EXAMPLE 34 Polymerization of Fluoroolefin TFE

An oligomer or low molecular weight polymer of TFE is made in carbondioxide by treating TFE with a nucleophile in carbon dioxide oxide toform a carbon dioxide-soluble product, such as trimer, tetramer,pentamer and hexamer. ##STR9##

EXAMPLE 35 Polymerization of Fluoroolefin HFP

An oligomer or low molecular weight polymer of hexafluoropropylene (HFP)is obtained by treating HFP with a nucleophile such as CsF in carbondioxide to form a soluble product in carbon dioxide.

EXAMPLE 36 Polymerization of Fluorostyrene Monomer STF Using a PalladiumCatalyst

A polymer is made in carbon dioxide under the homogeneous conditions bycopolymerizing a fluorinated monomer, such as: ##STR10## with carbonmonoxide using a palladium catalyst (for concentrations, see, e.g., M.Brookhart et al., J. Am. Chem. Soc. 114, pg. 5894 (1992)) to yield:##STR11##

EXAMPLE 37 Polymerization Using a Cosolvent

A polymerization is carried out in essentially the same manner asdescribed above, except that a cosolvent is added to carbon dioxide,such as less than about 5% by weight diglyme, to form a product solublein carbon dioxide.

EXAMPLE 38 Isolation of Polymer

A process is carried out in essentially the same manner as described inExamples 23-37 above, except that the product is isolated either all atonce by continuous reduction of pressure (venting) or is isolated infractions by controlled release or step-wise reduction of pressure andsubsequent collection and separation of the product.

EXAMPLE 39 Solubility of Fluoroolefin Polymer TFE

A low molecular weight polymer or oligomer of tetrafluoroethylene (TFE)with the structure: ##STR12## where n=1-5, was completely dissolved incarbon dioxide at 5000 psi and 60° C.

EXAMPLE 40 Solubility of Endcapped Fluoroolefin Polymer TFE

A low molecular weight polymer or oligomer of TFE which was endcappedwith ethylene, having the structure: ##STR13## where n=1-5, wasdissolved in carbon dioxide at 2000 psi and 60° C.

EXAMPLE 41 Solubility of Fluoroolefin Polymer CTFE

A low molecular weight polymer or oligomer of chlorotrifluoroethylene(CTFE) with the structure: ##STR14## was dissolved in carbon dioxideover a wide range of pressures and weight fractions. The phase diagramat 40° C. as shown in FIG. 1 was determined.

EXAMPLE 42 Solubility of Fluoroacrylate Polymer FOA

A high molecular weight polymer of (1,1-dihydroperfluorooctyl) acrylatewith the structure: ##STR15## was dissolved in carbon dioxide over awide range of pressures and weight fractions. The phase diagram at 60 °C. as shown in FIG. 2 was determined.

EXAMPLE 43 Solubility of Fluoroalkylene Oxide Polymer

A low molecular weight polymer or oligomer of hexafluoropropylene oxide(Krytox) with the structure: ##STR16## was dissolved in carbon dioxideat 5000 psi and 60° C.

EXAMPLE 44 Solubility of Fluorostyrene Polymer

A high molecular weight polymer of a fluoroalkysubstituted styrenemonomer with the structure: ##STR17## was dissolved in carbon dioxide at5000 psi and 60° C.

EXAMPLE 45 Solubility of Fluoroacrylate Polymer MeFOSEA

A high molecular weight polymer with the ##STR18## was dissolved incarbon dioxide at 5000 psi and 60° C.

EXAMPLE 46 Solubility of Fluoroolefin-Teflon Copolymer

A high molecular weight statistical copolymer of TFE andperfluoro-2,2-dimethyl-1,3-dioxole (Teflon AF 1600) having the followingstructure: ##STR19## was heated to 80° C. and pressurized to 6000 psiwith carbon dioxide. At these conditions two liquid phases formed--apolymer rich phase and a carbon dioxide rich phase. Upon venting, thecarbon dioxide-rich phase turned cloudy indicating that some of thepolymer dissolved in carbon dioxide.

EXAMPLE 47 Solubility of Fluorinated Vinyl Ether Polymer

A high molecular weight polymer with the structure: ##STR20## wasdissolved in carbon dioxide at 3490 psi at 60° C. The polymer alsodissolves in freon-113, but is insoluble in common organic solvents suchas THF, dichloromethane, and chloroform.

The foregoing examples are illustrative of the present invention, andare not to be taken as restrictive thereof. The invention is defined bythe following claims, with equivalents of the claims to be includedtherein.

That which is claimed is:
 1. A reaction mixture useful for carrying outthe polymerization of a fluoroacrylate monomer, said mixturecomprisingat least one fluoroacrylate monomer; a solvent comprisingcarbon dioxide fluid; and a polymerization initiator capable ofinitiating the polymerization of said fluoroacrylate monomer.
 2. Areaction mixture according to claim 1 further comprising a chaintransfer agent.
 3. A reaction mixture of claim 1, wherein saidfluoroacrylate monomer comprises a monomer of formula (I):

    H.sub.2 C═CR.sup.1 COO(CH.sub.2).sub.N R.sup.2         (I)

wherein: n is 1 or 2 R¹ is hydrogen or methyl; and R² is aperfluorinated aliphatic or perfluorinated aromatic group.
 4. A reactionmixture according to claim 3, wherein R² is a C1-C8 perfluoroalkyl or--CH₂ NR³ SO₂ R⁴, wherein R³ is C1-C2 alkyl and R⁴ is C1-C8perfluoroalkyl.
 5. A reaction mixture according to claim 1, wherein saidfluoroacrylate monomer is selected from the group consisting of:2-(N-ethylperfluorooctanesulfonamido) ethyl acrylate;2-(N-ethylperflooctanesulfonamido) ethyl methacrylate;2-(N-methylperfluorooctanesulfonamido) ethyl acrylate;2-(N-methylperflooctanesulfonamido) ethyl methacrylate;1,1-Dihydroperfluorooctyl acrylate; and 1,1-Dihydroperfluorooctylmethacrylate.
 6. A reaction mixture of claim 1 further comprising acomonomer.
 7. A reaction mixture useful for carrying out thepolymerization of a fluoroalkylene oxide monomer, said mixturecomprising:at least one fluoroalkylene oxide monomer; a solventcomprising carbon dioxide fluid; and a polymerization initiator usefulfor initiating the polymerization of said fluoroalkylene oxide monomer.8. A reaction mixture according to claim 7, wherein said fluoroalkyleneoxide monomer is selected from the group consisting ofperfluoropropylene oxide and perfluorocyclohexene oxide.
 9. A reactionmixture useful for carrying out the polymerization of a fluorostyrenemonomer, said mixture comprising:at least one fluorostyrene monomer; asolvent comprising carbon dioxide fluid; and a polymerization initiatorcapable of initiating the polymerization of said fluorostyrene monomer.10. A reaction mixture according to claim 9, wherein said fluorostyrenemonomer comprises a monomer of Formula (VI): ##STR21## wherein: R¹ andR² are each independently hydrogen, fluorine, or methyl;R³ is hydrogen,fluorine, methyl or perfluoromethyl; R⁴ is hydrogen, fluorine, or C1-C12perfluorinated aliphatic group; and wherein the 2, 3, 5, and 6 positionsof the aromatic styrene ring are each independently hydrogen orfluorine.
 11. A reaction mixture useful for carrying out thepolymerization of a fluorinated vinyl ether monomer, said mixturecomprisingat least one fluorinated vinyl ether monomer; a solventcomprising carbon dioxide fluid; and a polymerization initiator capableof initiating the polymerization of a fluorinated vinyl ether monomer.12. A reaction mixture according to claim 11, wherein said fluorinatedvinyl ether monomer comprises a monomer of Formula (IV):

    R.sup.1 R.sup.2 C═CR.sup.3 O(CH.sub.2).sub.n R         (IV)

wherein: n is O, 1 or 2; R¹, R² and R³ are each independently hydrogenor fluorine; and R is perfluorinated aliphatic or perfluorinatedaromatic group.
 13. A reaction mixture useful for carrying out thepolymerization of a fluoroolefin monomer, said mixture comprising:atleast one fluoroolefin monomer; a solvent comprising carbon dioxidefluid; and a polymerization initiator capable of initiating thepolymerization of fluoroolefin monomer.
 14. A reaction mixture accordingto claim 13, wherein said fluoroolefin monomer is selected from thegroup consisting of difluoroethylene, tetrafluoroethylene,hexafluoropropylene, chlorotrifluoroethylene, perfluoro-2,2 dimethyl-1,3-dioxole and mixtures thereof.
 15. A reaction mixture according toclaim 13, further comprising a chain transfer agent.
 16. A reactionaccording to claim 1, 7, 9, 11, or 13, wherein said carbon dioxide fluidis liquid carbon dioxide.
 17. A reaction mixture according to claim 1,7, 9, 11, or 13, wherein said carbon dioxide fluid is supercriticalcarbon dioxide.
 18. A single-phase solution comprising:a fluoroacrylatepolymer; and a solvent comprising carbon dioxide fluid.
 19. A solutionaccording to claim 18, further comprising a chain transfer agent.
 20. Asolution of claim 18, wherein said fluoroacrylate polymer comprisesmonomers of formula (I):

    H.sub.2 C═CR.sup.1 COO(CH.sub.2).sub.n R.sup.2         (I)

wherein: n is 1 or 2; R¹ is hydrogen or methyl; and R² is aperfluorinated aliphatic or perfluorinated aromatic group.
 21. Asolution according to claim 20, wherein R² is a C1-C8 perfluoroalkyl or--CH₂ NR³ SO₂ R⁴, wherein R³ is C1-C2 alkyl and R⁴ is C1-C8perfluoroalkyl.
 22. A solution according to claim 18, wherein saidpolymer comprises a copolymer.
 23. A solution according to claim 18,wherein said fluoroacrylate polymer comprises monomers selected from thegroup consisting of:2-(N-ethylperfluorooctanesulfonamido) ethylacrylate; 2-(N-ethylperflooctanesulfonamido) ethyl methacrylate;2-(N-methylperfluorooctanesulfonamido) ethyl acrylate;2-(N-methylperflooctanesulfonamido) ethyl methacrylate;1,1-Dihydroperfluorooctyl acrylate; and 1,1-Dihydroperfluorooctylmethacrylate.
 24. A single-phase solution comprising:a fluorostyrenepolymer; and a solvent comprising carbon dioxide fluid.
 25. A solutionaccording to claim 24, wherein said fluorostyrene polymer comprisesmonomers of Formula (VI): ##STR22## wherein: R² and R² are eachindependently hydrogen, fluorine, or methyl;R³ is hydrogen, fluorine,methyl or perfluoromethyl; R⁴ is hydrogen, fluorine, or C1-C12perfluorinated aliphatic group; and wherein the 2, 3, 5, and 6 positionsof the aromatic styrene ring are each independently hydrogen orfluorine.
 26. A single-phase solution comprising:a fluorinated vinylether polymer; and a solvent comprising carbon dioxide fluid.
 27. Asolution according to claim 26, wherein said fluorinated vinyl etherpolymer comprises monomers of Formula (IV):

    R.sup.1 R.sup.2 C═CR.sup.3 O(CH.sub.2).sub.n R         (IV)

wherein: n is O, 1 or 2; R¹, R² and R³ are each independently hydrogenor fluorine; and R is perfluorinated aliphatic or perfluorinatedaromatic group.
 28. A single-phase solution comprising:a fluoroolefinpolymer; and a solvent comprising carbon dioxide fluid.
 29. A solutionaccording to claim 28, wherein said fluoroolefin polymer comprisesmonomers selected from the group consisting of difluoroethylene,tetrafluoroethylene, hexafluoropropylene, chlorotrifluoroethylene,perfluoro-2,2 dimethyl-1,3-dioxole and mixtures thereof.
 30. A solutionaccording to claim 28, further comprising a chain transfer agent.
 31. Asolution according to claim 28, wherein said fluoroolefin polymer is anamorphous fluoroolefin copolymer.